This invention relates to an improvement in conventional carburetors used in conjunction with internal combustion engines. The basic purpose of a carburetor is to mix a hydrocarbon fuel such as gasoline and air to form a combustible mixture to power the pistons of an engine. A theoretically perfect carburetor should vaporize the fuel completely as it is discharged at the main fuel nozzle of the carburetor and should maintain the vaporized condition of the fuel through its delivery to the engine cylinders. However, such perfect vaporization exists only in theory.
Droplets of unvaporized gasoline are considerably heavier than the gaseous mixture with which they are traveling. Their greater inertia causes them to continue in the direction they are moving when the mixture turns to follow a passage or to enter another passage. If possible, the heavier particles continue straight ahead until they reach a dead end, rather than to make the desired turns. This results in the center cylinders of a cylinder bank in many engines being run on a richer mixture than the end cylinders. Better mixture distribution is one argument in favor of special multiple carburetors and specially "tuned" intake manifolds.
Good mixture distribution is important to smooth engine operation, even throttle response, reasonable fuel mileage and decreased exhaust emissions. Engine manufacturers to date have attempted to correct this problem by heating the mixture of fuel and air as it leaves the carburetor, thereby attempting to more completely vaporize the fuel in the mixture. This is typically done by routing exhaust gases to heat the intake manifold. Heat also is applied by many manufacturers by using a heated air cleaner which sends hot air to the carburetor on a cold engine and shortens the warmup time.
The area of the manifold that is heated is directly below the carburetor. This causes the mixture of gasoline and air to pass through a high temperature area immediately after leaving the carburetor. If the temeperature is high enough, most of the fuel will theoretically remain vaporized on its way to the cylinders.
The application of heat at the intake manifold does not work as effectively in practice as in theory. First, there is a large volume of air and fuel which must be heated as it passes rapidly along the intake manifold walls. The retention period for the mixture within the limited space available at the conventional intake manifold is very brief and there is not much opportunity to thoroughly heat the large volume of fuel-air mixture. Furthermore, more heat will obviously be applied to that portion of the mixture adjacent to the intake manifold walls than to the inner volume of the mixture.
Heated intake manifolds improve the operation of an engine, but do not assist in improving the power output. In a full throttle condition, an engine will develop more power if the air-fuel mixture is cool rather than heated. A cool mixture is more dense than a warm mixture, which means that if the mixture is cool more gasoline and air can be packed into the combustion chamber than is possible when using a mixture that has been thinned out by heat. Thus for maximum horsepower, the engine must be warm and the mixture of fuel and gasoline must be cool.
Devices for heating the mixture of gasoline and air in an attempt to fully vaporize the mixture prior to introduction into the intake manifold have been disclosed in prior patents in many different forms. U.S. Pat. No. 1,124,706 to Conwell shows a finned heat exchanger interposed between a carburetor and the intake manifold. The heat exchanger is heated by exhaust gases. Similarly, U.S. Pat. No. 3,150,652 to Hollabuagh utilizes heat from the cooling system to add heat between a carburetor and an intake manifold. It specifically describes valves that control the application of the heat. Another similar arrangement using heat from the exhaust manifold is shown in U.S. Patent 3,042,016 to Christian.
Another approach indicated by prior patents is to apply heat to the gasoline prior to its introduction into the venturi or throat of the carburetor. U.S. Pat. No. 1,684,246 to Salve shows a helical groove through which an initial mixture of air and the incoming fuel is heated by an electrical heating element as it passes from the float chamber to the main mixing chamber of the carburetor. U.S. Pat. No. 1,973,362 discloses a heating element which operates in a similar manner.
The present disclosure utilizes a simple diverting heat exchanger to thoroughly vaporize all of the incoming atomized gasoline, along with a portion of the incoming air. It interrupts the normal flow of the mixture through the venturi of the carburetor, diverting it through an elongated passageway where heat is applied to the mixture to completely vaporize the gasoline. This is preferable to heating of the new gasoline, which results in loss of evaporated gasoline and causes flooding of the engine when it is warm. This device eliminates the need for the application of heat to the intake manifold. It allows the engine to be run on a cooler mixture than is practical under present engine design.